lkml.org 
[lkml]   [2020]   [Jan]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] rbd: optimize barrier usage for Rmw atomic bitops
On Wed, Jan 29, 2020 at 7:23 PM Davidlohr Bueso <dave@stgolabs.net> wrote:
>
> For both set and clear_bit, we can avoid the unnecessary barrier
> on non LL/SC architectures, such as x86. Instead, use the
> smp_mb__{before,after}_atomic() calls.
>
> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
> ---
> drivers/block/rbd.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index 2b184563cd32..7bc79b2b8f65 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -1371,13 +1371,13 @@ static void rbd_osd_submit(struct ceph_osd_request *osd_req)
> static void img_request_layered_set(struct rbd_img_request *img_request)
> {
> set_bit(IMG_REQ_LAYERED, &img_request->flags);
> - smp_mb();
> + smp_mb__after_atomic();
> }
>
> static void img_request_layered_clear(struct rbd_img_request *img_request)
> {
> clear_bit(IMG_REQ_LAYERED, &img_request->flags);
> - smp_mb();
> + smp_mb__after_atomic();
> }
>
> static bool img_request_layered_test(struct rbd_img_request *img_request)

Hi Davidlohr,

I don't think these barriers are needed at all. I'll remove them.

Thanks,

Ilya

\
 
 \ /
  Last update: 2020-01-30 13:53    [W:0.052 / U:0.528 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site